Method of manufacturing manganese oxide pellets

ABSTRACT

Manganese oxide pellets are produced by forming a finely divided mixture of manganese ore, a carbonaceous fuel such as coke, and an addition agent which will form gaseous products on heating, and heating the balls at a temperature and for a time sufficient to partially reduce the manganese ore and obtain the required porosity. The pellets may be subjected to an additional step of heating the partially reduced pellets in the presence of a reducing gas at a temperature and for a time sufficient to reduce a major portion of the manganese content to manganous oxide.

' llnite atent tates 11111111 1451 Jan. 116, 1972 [54]METHQDUF'MANUFACTURING 3,235,371 2/1966 MANGANESE OXllDE PELLETS 3,9518/1967 3,375,097 3/1968 [72] Inventor: Vincent H. K. Chu, Bethlehem, Pa.3,352,635 11/1967 [73] Assignee: Bethlehem Steel Corporation 34676O29/1969 3,486,880 12/1969 [22] Filed: July 7, 1969 OTHER PUBLICATIONS[21] Appl. No.: 839,679

Nodulization & Pelletization of Fluorite Floation Concen- Related U.S.Application Data trates by H. Kenworthy, Report of Investigations 4829,U.S. Dt. It',D.l9l, .l,4,7,9,l0&ft {62] 0111151611 or Ser. No. 642,182,May 29, 1967, abanpages of the emf BC 5 pp cloned.

Prima Examiner-Allen B. Curtis [52] U.S. Cl.... ..75/3, 23/145, 264/44Almmg joseph O,Keefe [51] Int. Cl ..C011g 45/02 [58] Field ofSearch..75/3,4, 80, 20 F; 23/145; [57] ABSTRACT Manganese oxide pellets areproduced by forming a finely di- [56] References Cited vided mixture ofmanganese ore, a carbonaceous fuel such as 1 coke, and an addition agentwhich will form gaseous products UNITED STATES PATENTS on heating, andheating the balls at a temperature and for a time sufficient topartially reduce the manganese ore and ob- 1,109,448 9/1914Messerschm1dt ..23/214 min the required porosity The pellets may besubjected 0 an 210851052 6/1937 Taylor 75/20 F additional step ofheating the partially reduced pellets in the 2'136096 1 H1938 Benfler et"75/20 F presence ofa reducing gas at a temperature and for a time suf-2*9l4395 1 H1959 Dawes "75/3 X ficient to reduce a major portion of themanganese content to 2,961,411 11/1960 Klugh ..75/4 X manganous Oxide2,986,461 5/1961 Menegoz et al .....75/8O 3,219,436 11/1965 Heitmann etal 1.75/3 X 8 Claims, N0 Drawings METHOD OH MANUFACTURING MANGANESEOXIDE PELLETS CROSS-REFERENCES TO RELATED APPLICATIONS This is adivisional application of my original application Ser. No. 642,l82 filedMay 29, 1967 and entitled High- Porosity Manganese Oxide Pellets andMethod of Manufacturing Same, abandoned for continuation, Ser. No.871,599 filed Nov. 3. 1969, now abandoned.

BACKGROUND OF THE INVENTION It is known in the art that manganous oxideis an excellent acceptor of sulfur and may be used to remove sulfur fromsolid sulfur-containing materials, for example carbonaceous fuels suchas coltc pellets. The manganous oxide sulfur acceptor is made fromhigh-purity manganie oxide ores such as pyro- Iusitc, Ramsdellite andthe like. Most of these ores are not readily accessible and generallymust be briquetted, calcined, and crushed to a fine particle size priorto their use. Ramsdellite may, however, because of its inherent strengthbe calcined without briquetting after crushing the ore to a fineparticle size. See US. Pat. No. 2,950,231. Because of their fineparticle size, these ores require special techniques in materialhandling.

The object of this invention is to provide a method for manufacturingporous manganese-containing pellets which can be used as acceptors toremove sulfur from solid sulfurcontaining materials.

SUMMARY OF THE INVENTION The invention in its broadest aspect includesmixing a suitable amount of a carbonaceous-bearing reducing agent forexample anthracite eoal, bituminous coal, coke, petroleum coke, or cokebreeze, a finely divided manganese ore or concentrate and a sufficientamount of a suitable addition agent for example an alkaline metal saltof carboxyl methylcellulose, balling the mixture and heating the ballsat elevated temperatures to cause the carbonaceous-bearing material topartially reduce the manganese ore. During heating, gaseous products,for example carbon dioxide, are evolved. During this step, the additionagent breaks down also, forming gaseous products, for example carbondioxide. The gaseous products escaping from the interior of the pelletsform voids or pores in the pellets.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a more detailed descriptionof the invention, it has been found that oxidic and carbonate manganeseores may be processed into pellets. To pelletize these ores, the rawmaterials described above must be crushed to a suitable size; forexample, such that 65 percent of the particles will pass a 325 meshTyler Sieve Size. Typical ores or concentrates which may be used in theprocess may have the following chemical compositions:

Mn(%l (IO-107a) Fc(%) SiO2(%) AI O CaO(%) MgO(%) C(%) salt of earboxylmethylcellulose. The mixture is formed into balls. It may be desirableto add a small amount of a binder such as bentonite to the mixture, forexample between about 5 pounds and about pounds per ton of ore to givethe balls g reen strength. The green balls are heated ata temperatureand for a time sufficient to produce relatively hard pellets. During theheating step, the carbonaceous material reacts with the manganese ore topartially reduce the ore to manganous'manganite (Mno-Mn tl Somemanganous ferrite M nO- F e 0 may be formed if the ore containssufficient iron Gaseous products, primarily carbon dioxide, are formedin the reaction. The carbon methyl cellulose salt also brealts down toform gaseous products, suehas carbon dioxide. The gaseous products, inescaping from interior of the pellets outwardly to the surface of thepellets, form minute passages or pores. The addition agent can bedescribed as a pore-forming agent. Pellets produced according to theprocess of the invention develop a porosity of not less than about 45percent during the heating step.

It has also been found that by subjecting the pellets to a secondheating step, in the presence of a reducing gas, the

manganese oxide can be further reduced to obtain pellets which aresubstantially all manganous oxide (MnO), and have a porosity of not lessthan about 60 percent. These pellets can then be used as sulfuracceptors to remove a portion of the sulfur in solid, sulfur-containingmaterials such as colre pellets, or metallized iron-ore pellets. Thesolid, sulfur-containing materials are mixed with the manganous oxidepellets. The mixture is heated at a suitable temperature, for example,between about l,l00 F. to about l,650 F. and a gas containing hydrogenis passed through the mixture. The sulfur passes from the solid,sulfur-containing material to the manganous oxide pellets.

The amount of carbonaceous material required to partially reduce, and toassist in forming pores in the manganese ore pellets in the initialheating step may vary over a wide range, for example from about 600pounds to about 1,000 pounds per ton of manganese ore with 800* pounds apreferred amount. Too large an amount of carbonaceous material added tothe ore will result in the pellets becoming too hot causing them to fusetogether to form clin'kers. Too little carbonaceous material added tothe manganese ore will result in insufiicient reduction of the ore andinsufficient porosity.

The amount of decomposable addition agent which should be added may bebetween about 9 pounds and about l3.5 pounds per ton of manganese ore.

The porosity of the pellets is determined by the following formula:

true density-apparent density X true density Porosity where the apparentdensity is obtained by the well known mercury method and the truedensity is determined by the standard air pycnometer method.

In an example of the invention a synthetic ore mixture of the followinganalysis was used:

Mn(%) Fe(%) sio, Al 0 A balling mix was then made having the followingcomposition:

Synthetic ore mix (65% 32SMesh Tyler Sieve Sizeb 2,000 parts Anthracitecoal 200-Mesh Tyler Sieve Size) 800 parts Sodium Salt ofCarboxylMethylcellulose l2 parts Bentonlte 10 parts The mix was hailed in theconventional manner to form balls between one-quarter inch and one-halfinch in diameter.

Separate portions of the balls were fired in a muffle furnace All thefired pellets developed a porosity of 52.4 percent or more. The majormineralogical constituent of the pellets was manganous ferrite (Mno-Fe owith the minor constituent being MnO-SiO A portion of the fired pelletswas then activated by heating the pellets to within the temperaturerange of l,600l ,650 F. for from 20 to 30 minutes while carbon monoxidewas passed through the bed. All of the pellets were found to have aporosity of 63.1 percent or more with the major mineralogicalconstituent now being manganous oxide (MnO).

A mixture of metallized iron ore pellets and the activated manganousoxide pellets was heated at l,650 F. for 1 hour in the presence ofhydrogen gas. The sulfur content of the metallized iron ore pellets wasreduced from 0.65 to 0.28 percent and the sulfur content of themanganous oxide pellets was increased from 0.004 to 0.305 percent.

In another specific example of the invention a mix of the followingcomposition was made:

Amapa ore (65% -325-mesh) (Mn content 31.5%) 2,000 parts Anthracite(200-mesh) 800 parts Sodium Salt of Carboxyl Methylcellulose 12 partsBentonite l parts The mix was formed into balls one-quarter inch indiameter in the conventional manner. Separate portions of the balls wereheated in the presence of air under the following conditions:

The pellets had a porosity of not less than 51.4 percent and the majorconstituent as determined by X-ray identification was manganousmanganite (MnO-Mn O The pellets were then activated by heating at 1,600F. for 30 minutes in the presence of CO gas. The porosity of the pelletswas found to be not less than 66.5 percent and the major constituent asdetermined by X-ray identification was found to be manganous oxide(MnO).

A mixture of metallized iron ore pellets and the activated manganousoxide pellets was made. The bed of the mixed pellets was heated at l,650F. for 1 hour in the presence of hydrogen gas passed therethrough. Thesulfur content of the metallized iron ore pellets was reduced from 0.13to 0.035 percent while the sulfur content of the manganous oxide pelletswas increased from 0.005 to 0.13 percent.

It has been suggested that the manganese oxide pellets of the inventionmay be used as charge material in the production of ferromanganesealloys.

In this specification, wherever percentages are referred to, suchpercentages are by weight except as otherwise indicated.

lclaim:

1. Method of manufacturing pellets consisting essentially of porousmanganese oxides in which a major portion of said manganese oxides ismanganous oxide and the porosity of said pellets is not less than about45 percent comprising:

a. preparing a finely divided mixture of manganese ore, a

carbonaceous reducing agent and a pore-fonning addition agent whichwill, upon heating, decompose to form gases,

b. forming the mixture into balls, and

c. heating the balls at a temperature and for a time sufficient toreduce a major portion of the manganese oxides to manganous oxide and todecompose said pore-forming addition agent.

2. Method according to claim 1 in which the manganese content of the oreis not less than about 30 percent.

3. Method of manufacturing pellets consisting essentially of porousmanganese oxides, in which a major portion of said manganese oxides ismanganous oxide and the porosity of said pellets is not less than about45 percent comprising:

a. preparing a finely divided mixture of manganese ore, at least onecarbonaceous reducing agent taken from the group consisting essentiallyof anthracite coal, bituminous coal, coke, coke breeze and petroleumcoke, and at least one pore-forming addition agent taken from the groupconsisting essentially of an alkaline metal salt of carboxylmethylcellulose,

b. forming the mixture into balls, and

c. heating the balls at a temperature within the range of I about 1,950to about 2,200 F. for a time sufficient to reduce a major portion of themanganese oxides to manganous oxide and to decompose said pore-formingaddition agent.

4. Method according to"claim 3 in which the manganese content of the oreis not less than about 30 percent, the amount of carbonaceous materialis between 600 and 1,000 pounds per ton of ore and the amount ofalkaline metal salt of carboxyl methylcellulose is between 9 and 13.5pounds per ton of ore.

5. Method according to claim 3, including the further step of d. heatingthe pellets in the presence of a reducing gas at a temperature and for atime sufficient to reduce substantially all the manganese oxides tomanganous oxide.

6. Method according to claim 4, including the further step of d. heatingthe pellets in the presence of a reducing gas at a temperature and for atime sufiicient to reduce the major portion of the manganese content tomanganous oxide.

7. Method according to claim 5 in which step (d) is carried out in thetemperature range of l,600 to l,700 F.

8. Method according to claim 6 in which step (d) is carried out in thetemperature range of l,600 to l,700 F.

2. Method according to claim 1 in which the manganese content of the oreis not less than about 30 percent.
 3. Method of manufacturing pelletsconsisting essentially of porous manganese oxides, in which a majorportion of said manganese oxides is manganous oxide and the porosity ofsaid pellets is not less than about 45 percent comprising: a. preparinga finely divided mixture of manganese ore, at least one carbonaceousreducing agent taken from the group consisting essentially of anthracitecoal, bituminous coal, coke, coke breeze and petroleum coke, and atleast one pore-forming addition agent taken from the group consistingessentially of an alkaline metal salt of carboxyl methylcellulose, b.forming the mixture into balls, and c. heating the balls at atemperature within the range of about 1,950* to about 2,200* F. for atime sufficient to reduce a major portion of the manganese oxides tomanganous oxide and to decompose said pore-forming addition agent. 4.Method according to claim 3 in which the manganese content of the ore isnot less than about 30 percent, the amount of carbonaceous material isbetween 600 and 1,000 pounds per ton of ore and the amount of alkalinemetal salt of carboxyl methylcellulose is between 9 and 13.5 pounds perton of ore.
 5. Method according to claim 3, including the further stepof d. heating the pellets in the presence of a reducing gas at atemperature and for a time sufficient to reduce substantially all themanganese oxides to manganous oxide.
 6. Method according to claim 4,including the further step of d. heating the pellets in the presence ofa reducing gas at a temperature and for a time sufficient to reduce themajor portion of the manganese content to manganous oxide.
 7. Methodaccording to claim 5 in which step (d) is carried out in the temperaturerange of 1,600* to 1,700* F.
 8. Method according to claim 6 in whichstep (d) is carried out in the temperature range of 1,600* to 1,700* F.